ERR AG® Me 
Page 220 (Physics, p. 46). Under the head of Velocity of Efflux the following paragraph was 
omitted ; it ought to be inserted after the description of Plate 17, Fig. 33. 
The Swimmer of Prony (fig. 35) is an apparatus employed for obtaining a constant height of 
pressure of water. C is a box floating in the vessel, D, and supporting, by means of the 
rods A, B, a second box, G (below the aperture, E, of the vessel, D), into which all the water 
flowing from D is received through the funnel, F. The height of pressure in D will thereby 
remain unchanged, as the weight of the box, G, increased at the rate of the efflux from D, will 
draw down the box, C, so as to replace the water which has passed into G. 
